1. Field of the Invention
The present invention relates to an apparatus for non-invasively monitoring a supraventricular extrasystole as one of state changes of the excitation conducting system of the heat by use of electrocardiogram information and pulse-wave information.
2. Related art
The non-invasive monitoring apparatus uses mainly the information of electrocardiograms, arterial oxygen saturation, blood pressure measured by the oscillometric blood-pressure measuring apparatus and the like as parameters representative of dynamic states of a patient. Of those parameters, electrocardiogram information, arterial oxygen saturation and the like may continuously be measured. In particular the electrocardiogram information is used as a parameter sensitively representing a change of a dynamic state of the patient.
Thus, the electrocardiogram information has been used as the continuously monitoring parameter. An arrhythmia of the patient is monitored by use of the waveforms and heat rate on the electrocardiogram. The monitoring based on only the electrocardiogram has the following problems.
A supraventricular extrasystole, if it frequently occurs, indicates a symptom of a disease of the atrium or a premonitary symptom of the atrial fibrillation. Because of this, it must be detected. In detecting the supraventricular extrasystole, one will encounter the following difficulties. A QRS wave caused by the normal sinus rhythm contraction as a normal contraction is the same as by the supraventricular extrasystole. Therefore, it is impossible to discriminate between the normal sinus rhythm contraction and the supraventricular extrasystole by use of the QRS wave alone. The supraventricular extrasystole does not always appear as a clear variation of the R--R interval (R-wave to R wave interval). Therefore, it is often difficult to discriminate between the R--R interval variation by the supraventricular extrasystole and that by breathing. A discrimination between the normal sinus rhythm contraction and the supraventricular extrasystole may be made on the basis of a waveshape of the P wave. The signal level of the P wave is small. Therefore, the P wave sometimes sinks into the preceding T wave. The waveshape of the P wave varies depending on a location where the extrasystole takes place. For this reason, it is difficult to discriminate between the sinus rhythm contraction and the supraventricular extrasystole.
Thus, it is difficult to detect the supraventricular extrasystole using only the electrocardiogram information for the parameter continuously obtained in non-invasive manner.